I enjoy ATC a lot and LAX is my favorite to do ATC for but there are a couple of commands I would love to have. One would be in essence telling pilots that a certain runway is being used for landings only and the other is for takeoff.
Another would be along the lines of - that runway is inactive please go to the other end of the airport.
While this isn’t the nicest button, I would really really really like a “You’re an idiot” button with the power to freeze their plane or something. So many pilots just do their own thing. There was this one pilot who was at the front of the line. I told him 8 times to lineup and wait. He never moved. Finally I just tell him to take off. Still doesn’t move! I tell him another 6 times to take off. Finally the people behind him just start taking off. Of course once one person breaks the rules, 6 planes decide to all take off together. .